I quest with my intial crew of 5 (Pally + 4 Shammies), I ran some instances but nothing really reliable as my tank sucked. At 77 I moved to Icecrown and did the dailies everyday and leveled to 80 in no time.

I then leveled a DK solo and quested him solo until 68, hit Northrend and then did the quests till 71 and then AOE out of party grinded him from 71-80 in about 30 hours.